Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$19.86	12.399%	$22.3224	$22.32	$22.30	$22.30
Purchase #2	$167.86	8.809%	$182.6468	$182.65	$182.65	$182.60
Purchase #3	$61.25	6.866%	$65.4554	$65.46	$65.45	$65.50
Purchase #4	$164.86	6.679%	$175.871	$175.87	$175.85	$175.90
Purchase #5	$159.50	12.354%	$179.2046	$179.20	$179.20	$179.20
Purchase #6	$222.65	10.628%	$246.3132	$246.31	$246.30	$246.30
Purchase #7	$229.90	9.578%	$251.9198	$251.92	$251.90	$251.90
7 purchase totals =	$1,025.88		$1,123.7332	$1,123.73	$1,123.65	$1,123.70